Recorder for radio locators



l June 17, 1947. T, T, EATON RECORDER FOR RADIO LoCAToRs Filed Aug. 30, 1943 2 Sheets- Sheet l NQN o NQ `Pune 17, 1947. T. T. EATON 2,422,295

RECORDER FOR RADIO LOCATORS Filed Aug. 50, 1943 2 Sheets-Sheet 2 .Sme/T65 rues #fics/MM5 @ico/P052 nvenfor Gttorneg .SONY/WHG BEHM TPHCE- Patented June 17, 1947 accomuna Fon mimo Loca'roas Y Thomas T. Eaton, Haddon Heights, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application August 30, 1943, Serial No. 500,741

My invention relates to radio locator systems and to methods of and means forrrecording the object location information received by an object locator system.

An object of the invention is to provide an improved method of and means for recording radio locator information on a low speed recorder such as a facsimile recorder.

Another object of the invention is to provide an improved method of and means for obtaining a record that indicates clearly the location of objects to the right and to the left of the radio locator system.

Still another object of the invention is to provide an improved method of and means for obtaining amplied radio locator signals suitable for operating a recorder.

The invention will be described as applied to a radio locator system of the pulse-echo type having a transmitter that is switched alternately to a pair of antennas that radiate to the right and to the left, respectively. The reected pulses are applied to a cathode ray indicator tube which has its time sweep axis displaced in the vertical direction synchronously with the left-right antenna switching. The resulting right" and left images on the screen of the indicator tube are projected, by means of a suitable lens system, upon two bars of storage or mosaic elements of a cathode ray storage tube. The stored images are then reconverted to electrical signals by scanning the storage mosaic slowly along the length of the bars with an electron beam and simultaneously deflecting the beam transversely at a rapid rate across each mosaic bar and beyond its edges. These signals are then amplied by an alternating-current amplifier and supplied to a recorder in which the scanning is synchronous with the scanning of the storage mosaic.

By deilecting the electron beam beyond the edges of a mosaic bar as described, it is possible to use an A.C. amplifier and thus avoid the dimculties ordinarily encountered in using a high gain direct-current amplier.

Preferably, the two mosaic bars are scanned in opposite directions so that the "right" and Ileft images may be recorded to the right and tothe left, respectively, of a center line representing zero distance.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which y Figure 1 is a circuit and block diagram of a pulse-echo system embodying my invention,

7 Claims. (Cl. Z50-1.62)

Figure 1a is a view of the screen end of the cathode ray indicator tube shown in Fig. 1,

Figure 1b is a view of the record that is obtained when the image on the indicator tube is as shown in Fig. 1a,

Figure 2 is a view in perspective of the cathode ray indicator and storage tubes which shows the direction of scanning in the two tubes,

Figure 3 is a view of the scanned side of the storage screen of the storage tube of Figs. 1 and 2,

Figures 4, 5 and 6 are graphs that are referred to in explaining the'invention. and

Figure 7 is a block and circuit diagram of an amplifier and a detector that may be employed in the circuit of Fig. 1 for supplying signal to the recorder.

In the several gures, similar parts are indicated by similar reference characters.

Referring to Fig. 1 of the drawing, a high frequency radio transmitter I0 is pulse modulated by means of a pulse modulator` I I and a pulse generator I2 to radiate short radio pulses alternately to the right and to the left from a pair of antennas I3 and I4, respectively. The keying or modulating pulses preferably are applied to the keyer II through a delay circuit I5. The antennas I3 and Il may be two dipoles in parabolic reectors which are positioned to radiate to the right and to the left. The antennas I3 and I4 are connected alternately to the transmitter by means of suitable left-right switching means I1 which may be driven by a motor (not shown). The transmitted pulses may occur at the rate of 1'700 per second and have a duration of 0.3 microsecond; the switching from left to rightvmay Y.

occur at the rateof 30 per second, that is, on 1eft" fori/ao second and on the right for 1/en second. These values are given merely by way of example. I

The reflected pulses are picked up by a suitable antenna I8 and supplied to the receiver I9 which amplifies and demodulates them. They are then applied with positive polarity to the control grid 2l of a cathode ray tube 22 which is biased near electron beam cut-off.

The cathode ray tube 22 may be of conventional design having a iuorescent screen 23 and two pairs of deiiecting plates 24 and 26 positioned at right angles to each other. A sawtooth sweep or timing voltage is produced by a. sawtooth generator 21 and applied to the plates 24 to deflect the cathode ray horizontally at a repetition rate oi 1700 sweeps per second in the example being described.

A relay switch arm 28 is operated synchronous- 26 whereby the cathode ray of the tube 22 is del flected up or down to give an upper image of reflecting objects to the right when the antenna radiation is toward the right and to give a lower image of reflecting objects to the left when the antenna radiation is toward the left. Such images are illustrated in Fig. lq.- where objects A and B to the right and an object C to the left are indicated.

Preferably, the horizontal scanning line is widened, in effect, by also applying to the vertical 'deecting plates 26 a high frequency sine wave voltage from a suitable source 3|.

In order to record the reflecting object indications that appear on the fluorescent screen 23, the right and left images` are projected by means of a suitable lens system 32 upon a storage screen 33 of a cathode raystorage tube 34 such as a television pick-up tube of the low velocity beam type. As shown in Fig. 3, the storage screen 33 preferably comprises two bars 35 and 40 of mosaic or capacity elements. Thus the images are stored on the mosaic bars 35 and 40 whereby they may be scanned slowly enough in the horizontal direction (i. e., along their length) to obtain a signalthat can be recorded on a comparatively slow speed recorder.

Referring briefly to the structure of the tube 34, the tube has a low velocity beam gun comprising a cathode 36, a control grid 31, avfirst anode 39 and a second anode 4 I. Ring electrodes 42 and43 are provided to slow down the electrode beam as it approaches the storage screen 33. In the example illustrated, the signal taken off the screen 33 by the low velocity beam appears across an output resistor 44 which is connected between the back plate of the screen 33 and ground. The horizontal and Vertical deflections of the low velocity beam may be obtained by means of two pairs of deecting coils H and V, respectively.

The stored image on the mosaic 33 is scanned by means of a triangular current wave, represented by the graph 45, which is supplied to the horizontal deflecting coils H. In order to scan the right and left indicationsalternately, rectangular pulses of current are supplied to the vertical deecting coils V from a battery 46 through a switch arm 41 operated by a cam 48. The direction of scanning is indicated in Fig. 2 by the arrows on the dotted line 49, the scanning being in one direction yacross the "right indications and in the opposite direction across the left indications.

The high frequency transverse scanning of the mosaic bars 35 and 40 is obtained by supplying a sine wave defiecting current to the vertical deflecting coils V from an oscillator 5I. The output of oscillator 5I is applied between ground and the center point of the battery 46 through a transformer 52. The amplitude of this transverse sine wave deflection is suiiicient to deflect the electron beam off the mosaic bars whereby an electrical pulse is prcduced for each half cycle of the sine wave vdeflection where the beam is being deiiected transversely across mosaic elements that have object indications stored thereon.

The method of employing alternating-current amplification of the stored indications will be better understood by referring to Figs. 4, 5 and 6i--In Fig. 4 a stored indication is shown at C by the shaded area. Each time the electron beam s deflected off this area, a pulse is produced as a result of the output current falling to zero value. This is illustrated by the graph 60 in Fig. 5.v These pulses are supplied to an A.C. amplifier 56 (Fig. 1) which preferably is tuned to the repetition rate of these pulses. 'Ihe output of the amplifier 56 is an amplified voltage l simile recorder 53.

on the other side that functions as a back plate.

The desired mosaic bar design may then be ubtained by masking ofi the bar areas 35 and 40 and evaporating a conducting layer P (Fig. 3) of a metal such'as silver upon the rest of the mosaic surface. This conducting layer preferably is maintained at a low negative potential by means of a voltage source E so that the signal output of the storage tube will be zero when the electron beam is not on a sensitized mosaic area.

The signal output will, of course, also be zero when the electron beam `is scanning a region of a mosaic bar which has not had a light spot or object indication projected thereon.

The recorder 53 may be of a type commonly employed in facsimile systems. In the example illustrated, it is a carbon paper recorder comprising a, drum 54 having a spiral scanning strip thereon and having a printer bar (not shown) viich is actuated by the output of the rectifier The triangular scanning wave I45 is produced by means of a potentiometer 51 comprising a resistor 58 and an arm 59 that is rotated in synchronism with and at the sameI rate as the recorder drum 54, this rate being one-half revolution per second, for example. The potentiometer resistor -58 has its two halves connected in parallel with respect to a battery 6I whereby the defiecting current supplied from the arm 59 increases and then decreases as the arrn is rotated to produce the triangular current wave 45. The mechanical coupling of the scanning drum and the potentiometer arm is such that the recorder scans the left half of a paper strip 62 while the left image indications on the mosaic are being scanned in one direction and scans the right half of the paper while the right image indications on the mosaic are being scanned in the opposite direction. As a result the recorded image is of the character shown in Fig. 1b where the distances to objects at the right or at the left of the locator system are measured from the center or zero line of the paper strip 62.

The invention is not limited to the use of a mosaic screen having mosaic Ibars. For example, a conventional mosaic screen such as previously described may be employed without the addition of the evaporated coating or mask on the unused ning. ,.'I'his prevents the accumulation of undesired charges on the screen. Also, it may be noted that with no masking on the mosaic the effect ofv any stray light on the mosaic screen is greater than in the preferred double-mosaic-bar design.

As shown in Fig- '7, the amplifier 56 may comprise amplifier stages of the type each having a tuned plate circuit as indicated at 1I. The rectifier 55 may comprise a single rectifier tube, or, as

and directing it against said storage screen, means for causing each of a plurality of successive signal indications to -b`e stored on a certain area of said screen at some point along a distance axis thereon whereby the capacity elements at said points hold charges corresponding to said signal indications, means for deecting said beam across said certain area in the direction transverse to said distance axis at a fast repetition rate and for deflecting it across said certain area in the direction of said distance axis at a slow repetition rate, the deflection of said fast rate being of sufcient amplitude to deflect the beam beyond at least one edge of each of said certain area whereby an electrical impulse is produced each time the beam is defiected across charged capacity elements and beyond said edge, and whereby groups of said impulses, each group representative of one of said signal indications, may be amplified by an alternating-current amplifier,

2. In combination, a cathode ray storage tube having a storage screen comprising a multiplicity of capa-city elements each capable of storing a charge, means for producing a beam of electrons and directing it against said storage screen, means for causing each of a plurality of successive signal indications to be stored on a certain area of said screen at some point along a distance axis thereon whereby the capacity elements at said points hold charges corresponding to said signal indications, said certain area having a width that is narrow -compared with its length along said distance axis, means for defiecting said lbeam across said certain area in the direction of said width at a fast repetition rate and for deecting it across said certain area in the direction of said length at a slow repetition rate, the deflection at said fast rate being of sufficient amplitude to deflect the beam beyond at least one edge of each of said certain area whereby an electrical impulse isproduced each time the beam is deflected across charged capacity elements and beyond said edge, an alternating-current amplifier, and means for supplying said impulses to said amplifier whereby a plurality of impulses representative of each signal indication are amplified.

3. In combination, a cathode ray storage tube having a storage screen comprising a multiplicity of capacity elements each capable of storing a charge, means for producing a beam of electrons and directing it against said storage screen, means for transmitting successive radio pulses to a refiecting object, means for receiving the reflected pulses, means for causing each of a plurality of successive signal indications corresponding to said reflected pulses to be stored on a certain area of said screen at some point along a distance axis thereon whereby the capacity elements at said points hold charges corresponding to said signal indications, said certain area having a width that is narrow compared with its length along said distance axis, means for deiiecting said beam across said certain area in the direction of said width at a fast repetition rate and for deecting it across said certain area in the direction of said length at a slow repetition rate, the deflection at said fast rate being of suii'icient amplitude to deflect the Ibeam beyond at least one edge of each of said certain area whereby an electrical impulse is produced each time the beam is deflected across charged capacity elements and beyond said edge, an alternating-current amplifier, and means for amplifying said impulses by said amplifier whereby said reflectedl pulses may -be recorded.

4. In combination, a cathode ray storage tube, a storage screen having a storage surface containing a multiplicity of capacity elements each capable of storing a charge, the surface of said screen surrounding said storage surface being conducting, means for producing a beam of electrons and directing it against said storage screen, means for causing each of a plurality of successive signal indications to be stored on said storage surface at some point along a distance axis thereon whereby the capacity elements at said points hold charges corresponding to said signal indications, said storage surface having a width that is narrow compared with its length along said distance laxis, means for deiiecting said beam across said storage surface in the direction of said width at a fast repetition rate and for deflecting it across said storage surface in the direction of said length at a slow repetition rate, the deflection of said fast rate being of sufllcient amplitude to deflect the beam beyond at least one edge of each of said storage surface whereby an electrical impulse is produced each time the beam is deflected across charged capacity elements and beyond said edge, and whereby groups of said impulses, each group representative of one of said signal indications, may be amplified by an alternating-current amplifier.

5. The invention according to claim 4 wherein the conducting surface of said screen is main tained at a negative potential.

6. In combination, a cathode ray storage tube, a storage screen having two spaced storage surfaces each containing a multiplicity of capacity elements, each of said elements being capable of storing a charge, the remaining surface of said screen being conducting, means for producing a beam of electrons and directing it against said storage screen, means for causing a plurality of successive signal indications to be stored on said storage surfaces whereby the capacity elements in certain areas of said storage surfaces hold charges corresponding to said signal indications,

means for defiecting said beam at a fast repetition rate across said storage surfaces in the direction of their width and for deflecting it successively across said storage surfaces in the direction of their length at a slow repetition rate, the deection at said fast rate being of sufficient amplitude to deflect the beam beyond at least one edge of each of said storage surfaces whereby an electrical pulse is produced each time the beam is deflected beyond said edge, an alternating-current amplifler, and means for supplying said pulses to said amplifier for obtaining amplitied pulses for recording said signal indications.

7. A radio locator system comprising means for transmitting successive radio pulses in two directions toward reecting objects, means for receiving the reflected pulses, a cathode ray storage tube, a storage screen having two spaced storage surfaces each containing a multiplicity of capacity elements, each of said elements being :apable of storing a charge, the remaining surface of said screen being conducting, means for producing a beam of electrons and directing it. against said storage screen, means including said receiving means for causing a -plurality of successive signal indications corresponding to the pulses reflected from said two directions to be stored on said two storage surfaces, respectively, whereby the capacity elements in certain areas of saidstorage surfaces hold charges corresponding to said signal indications, means for de- Electing said beam at a fast repetition rate across said storage'surfacesvin the direction of their width and for deiiecting it successively across said storage surfaces in the direction of their 8 length at a slow repetition rate. the deflection at said fast rate being of sumcient amplitude to deect the beam beyond at least one edge oi each o1 said surface areas whereby an electrical pulse is produced each time the beam is deflected beyond said edge,gan alternating-current amplifier, and means for supplying said pulses to said amplifier for obtaining amplied pulses for recording said signal indications.

' THOMAS T. EATON.

REFEBENCS CITED yThe following references are of record in the le of this patent:

UNITED s'IfA'rEsv PATENTS Aiel Nov. 28, 

